Dispensing devices of this general type, as is well known in the art, are useful in the application of a variety of pasty or highly viscous products such as adhesives, joint filler agents, foams, sealants, molding compounds etc., whereas the products consist of two or more components to be stored separately, before use to be mixed however in order to start a chemical reaction between them, usually causing a solidification or hardening of the mass. In using the device, the content of the cartridge is pressed out of each barrel by actuation of a delivery plunger, the components flowing from the orifice into and through the attached mixer unit where they become closely intermixed. Usually the content of a cartridge is dispensed intermittently in several portions, whereas the components joined within the mixer will steadily react during the idle intervals. If the intervals are long enough, the mixer will become inoperable and will have to be replaced. This is due to the fact that the components will cure at the interface between the cartridge and the mixer and, due to diffusion, this curing will extend back in to the cartridge. This may hinder the detachment of the mixer (ordinarily left on the cartridge), but even worse, solidified particles or "clods" formed in the mass will block the further dispensing of the cartridge content and will cause defective application, such as rippled surface on articles, faulty joints, etc.
It is an object of the invention to eliminate these drawbacks and to afford unimpeded delivery of the cartridge content and faultless application thereof upon repeated replacement of the mixer unit and after extended time intervals between partial deliveries.
Dispersing and mixing combinations have been known in which fluids to be mixed have been dispensed by double barrelled syringe or caulking gun type dispensers (see e.g. U.S. Pat. Nos. 3,309,814, 4,041,463, and 4,538,920). These prior devices are included among those described above and have several specific drawbacks. The '814 patent employs a moving mixing element and it leaves the two fluids to be mixed in close juxtaposition at the delivery point of the syringe, and hence subject to cross-contamination. In addition, the mixer was not conveniently disposable, and leaves the orifice of the dispenser subject to contamination by admixture of the two fluids. The '463 patent discloses a disposable mixing device for use with a two barrelled dispenser and a baffle which extends into the mixer. Contamination between the two fluids at the orifice of the dispenser is avoided by a rubber seal. The '920 patent discloses a disposable mixing tube secured to a double barrelled syringe type dispenser in which a premix chamber is used to split each of the separate streams prior to their reaching the mixing elements. The disadvantages of this type of premixing are that it introduces a substantial pressure drop in the mixing line and does not cooperatively contribute to the mixing action of the stationary mixing elements further downstream.
The objects of this invention are to overcome some or all of the disadvantages of the prior art. More particularly, it is an object to provide a dispenser and disposable mixer combination in which cross-contamination between a plurality of fluids is avoided at the orifice end of a multibarrelled dispenser without substantial pressure loss. Still another object is to accomplish the foregoing objectives and at the same time direct the moving streams in such a way as to enhance the mixing action of the stationary mixing elements downstream.